Madagascar Rainbow

Quick summary

The Madagascar Rainbow is a lively, hardy schooling fish that rewards keepers with beautiful golden-olive colouring and active mid-water swimming. If you have a tank of 150 litres or more and enjoy watching a tight, energetic group interact, this species is an excellent choice for intermediate keepers or confident beginners.

🐠 Build a tank around this species

• Introduction
• Quick stats
• Appearance
• Natural habitat
• Tank size and setup
• Water parameters
• Filtration and equipment
• Diet and feeding
• Behaviour and temperament
• Tank mates
• Breeding
• Common diseases and health
• Frequently asked questions
• Related guides

Introduction

The Madagascar Rainbow, known scientifically as Bedotia madagascariensis, is one of those fish that quietly wins people over. It doesn’t have the instant “wow” factor of a neon-coloured cichlid or a fancy betta, but give it clean water, a proper school, and a well-planted tank, and it develops a subtle, shimmering beauty that photographs simply cannot capture. Males in good condition glow with olive-gold flanks, dark-edged fins, and a striking tail that catches the light as they spar and display for each other.

This species hails from the rivers and streams of eastern Madagascar, an island famous for its unique wildlife. In the aquarium hobby, the Madagascar Rainbow occupies a sweet spot: it is hardy enough for someone moving past their first “easy” community tank, yet interesting enough to hold the attention of experienced fishkeepers. It schools actively, breeds readily, and mixes well with a broad range of peaceful to semi-aggressive community fish. For planted tank enthusiasts, it adds constant movement to the mid-water column without uprooting or eating your aquascaping efforts.

If you are looking for a fish with personality, longevity, and relatively simple care requirements, the Madagascar Rainbow deserves a place on your shortlist. This guide covers everything you need to set up a tank, choose compatible neighbours, and keep your school thriving for years.

Appearance

The Madagascar Rainbow has a streamlined, laterally compressed body typical of the rainbowfish group, with a somewhat elongated shape and two distinct dorsal fins. Base body colour ranges from olive-green to golden-yellow, with a dark horizontal stripe running from the snout through the eye and along the midline of the flank. Scales often carry a faint iridescent sheen that shifts between blue, green, and gold depending on the angle of light. The fins are translucent to yellowish, edged in black or dark brown, and the caudal fin in mature specimens can develop bold black margins that make the tail look beautifully framed.

Males and females are fairly easy to tell apart once they reach maturity. Males tend to be larger, deeper-bodied, and more vividly coloured, with more pronounced black edging on the caudal and anal fins. During courtship and sparring, males intensify their colours noticeably. Females are slimmer, slightly paler, and have less dramatic fin edging. Both sexes display the characteristic lateral stripe, but it is often more prominent in females due to the lighter background colour of their flanks.

Natural habitat

Bedotia madagascariensis is endemic to the freshwater rivers and streams of eastern Madagascar, particularly in the forested highland and lowland drainages that flow toward the Indian Ocean. These waterways are typically clear to slightly tannin-stained, with moderate current flowing over rocky and sandy substrates. Overhanging vegetation and submerged roots provide shelter, while aquatic plants and algae-covered stones serve as foraging grounds. Water temperatures in these habitats are generally warm but not tropical-hot, sitting in the low to mid-20s Celsius for much of the year.

Understanding this habitat helps inform good aquarium practice. These fish evolved in well-oxygenated, gently flowing water with a neutral to slightly acidic pH. They are accustomed to dappled light filtered through forest canopy, not intense direct lighting. Perhaps most importantly, Madagascar’s freshwater ecosystems face serious threats from deforestation, pollution, and invasive species, so keeping and breeding this fish responsibly in captivity contributes, in a small way, to maintaining a viable population outside its increasingly pressured natural range.

Tank size and setup

A group of six Madagascar Rainbows should have a minimum of 150 litres, and a longer tank is preferable to a taller one since these fish are active horizontal swimmers. For each additional fish beyond six, add roughly 15 litres. A 120 cm long tank works beautifully for a group of eight to ten, leaving room for tankmates in the lower levels.

For substrate, a mix of fine gravel and sand mimics their natural stream bed. Darker substrates, such as black sand or dark river gravel, will show off their colouring much better than pale or white options. Include a handful of smooth river stones and a piece or two of driftwood to break up sightlines and create natural boundaries for sparring males. Avoid sharp-edged decorations that could damage fins during chasing.

Plants are strongly recommended. Hardy species such as Vallisneria spiralis, Cryptocoryne wendtii, Java fern (Microsorum pteropus), and Anubias barteri work well. Plant densely along the back and sides to give the fish a sense of security, but leave the central and front areas open for swimming. Floating plants like Amazon frogbit (Limnobium laevigatum) help diffuse bright light, which suits this species well.

Lighting should be moderate. If you are running bright LED fixtures for plant growth, floating plants or tall background stems like Hygrophila polysperma will provide welcome shaded zones. A gentle to moderate current across the tank, created by the filter outlet or a small powerhead, replicates their natural stream environment and keeps these fish looking their best.

Water parameters

Madagascar Rainbows are reasonably adaptable within these ranges but do best in clean, well-oxygenated water with stable parameters. They tolerate slightly harder water better than many soft-water species, which is good news for keepers with moderately hard tap water. Regular weekly water changes of 20 to 30 percent are important, both to keep nitrates low and to maintain the dissolved oxygen levels these stream-dwelling fish appreciate. Sudden swings in temperature or pH are far more dangerous than being a degree or two outside the ideal range, so consistency should be your priority.

Filtration and equipment

A good canister filter or a large hang-on-back filter is the best choice for a Madagascar Rainbow tank. Canister filters such as the Fluval 207 or Eheim Classic 350 provide strong biological and mechanical filtration while allowing you to direct the outlet to create a gentle current across the length of the tank. Sponge filters can work as supplementary filtration, especially in breeding setups, but they may not provide enough flow for the main display tank.

A reliable heater is recommended even though these fish tolerate cooler temperatures than many tropical species. An adjustable heater rated for your tank volume, something like the Eheim Jager or Fluval M series, ensures the temperature stays stable overnight and through seasonal changes. Set it at around 23 to 24 °C as a comfortable midpoint.

Invest in a quality water testing kit. The API Freshwater Master Test Kit is the hobby standard and covers ammonia, nitrite, nitrate, and pH. Test weekly while the tank is establishing and at least fortnightly once it is mature. A thermometer, either a digital probe or a reliable glass type, should be visible at a glance so you can spot heater malfunctions early.

Diet and feeding

In the wild, Madagascar Rainbows are omnivores that feed on small insects, insect larvae, crustaceans, algae, and plant matter drifting through the water column. They are not fussy eaters in captivity, which is one of their best qualities.

A high-quality flake or micro-pellet should form the staple diet. Brands like Hikari Micro Pellets, Northfin Community, or New Life Spectrum Small Fish Formula all work well. Supplement this two to three times per week with frozen or live foods: daphnia, baby brine shrimp, bloodworms, and mosquito larvae are all eagerly accepted. Occasional blanched spinach or spirulina flakes round out the vegetable portion of their diet.

Feed once or twice daily, offering only what the group can consume in about two minutes. These fish are enthusiastic surface and mid-water feeders, so food that floats or sinks slowly works best. Overfeeding is the easiest mistake to make with an active school since they always look hungry. Stick to small, measured portions and you will maintain better water quality and healthier fish.

Behaviour and temperament

Madagascar Rainbows are active, social fish that spend most of their time swimming back and forth through the mid-water column in a loose school. They are not a tightly coordinated shoaling species like rummy-nose tetras, but they clearly prefer each other’s company and will be visibly stressed or pale if kept alone or in very small numbers. A group of six is the minimum, and groups of eight to twelve really bring out the best behaviour.

Males regularly spar with each other in brief, mostly harmless displays. They flare their fins, intensify their colours, and swim parallel to a rival before one backs down. This sparring is one of the most entertaining aspects of keeping the species, and it rarely results in injury as long as the tank provides enough space and visual barriers. Having a higher ratio of females to males, around two females per male, reduces the intensity of male-on-male competition and prevents females from being harassed.

One quirk worth noting is that these fish can be a little skittish in the first few days after introduction, sometimes dashing into cover when the room lights change or when someone walks past the tank. This settles quickly as they grow accustomed to their surroundings, especially if there are plants and driftwood to retreat to.

Tank mates

Good tank mates

• Bristlenose Pleco (Ancistrus sp.) – peaceful bottom dweller that occupies a different level and helps with algae
• Cherry Barb (Puntius titteya) – calm, similarly sized barb that does well in planted community tanks
• Corydoras sterbai – gentle bottom feeder that thrives in the same temperature range
• Harlequin Rasbora (Trigonostigma heteromorpha) – peaceful mid-water schooler that complements without competing
• Kribensis (Pelvicachromis pulcher) – mild-mannered dwarf cichlid that stays in the lower tank regions
• Siamese Algae Eater (Crossocheilus oblongus) – active but peaceful, useful algae control
• Rummy-nose Tetra (Hemigrammus rhodostomus) – tight-schooling tetra that adds a different movement pattern

Fish to avoid

• Tiger Barb (Puntigrus tetrazona) – notorious fin nipper that will harass Madagascar Rainbows, especially during displays
• Oscar (Astronotus ocellatus) – far too large and predatory for a community with these rainbows
• Betta splendens (male) – territorial in confined spaces and may be stressed by the constant activity of a rainbow school
• Red-tail Shark (Epalzeorhynchos bicolor) – aggressive and territorial bottom-to-mid dweller that can bully mid-water fish
• Green Terror (Andinoacara rivulatus) – large, aggressive cichlid that will dominate and potentially injure smaller tankmates

Breeding

Breeding Madagascar Rainbows in captivity is quite achievable and a rewarding project for anyone with a spare tank. Sexing is straightforward in mature fish: males are larger and more colourful with bolder fin margins, while females are slimmer with rounder bellies when carrying eggs.

To condition a breeding group, feed generously with live or frozen foods such as daphnia and brine shrimp for two to three weeks. A separate breeding tank of 60 to 80 litres works best, with a temperature around 24 to 25 °C and a pH close to 7.0. Add fine-leaved plants or spawning mops, as the fish scatter adhesive eggs among vegetation. Java moss is an ideal spawning medium because eggs lodge in its dense structure where adults are less likely to find and eat them.

Spawning usually takes place in the morning. The male courts the female with intense colour displays, and the pair swims side by side through the spawning medium, releasing eggs and milt simultaneously. A healthy female can deposit 20 to 50 eggs in a single spawning session, and pairs may spawn on consecutive mornings over several days.

After spawning, remove the adults or transfer the spawning mops and plants to a separate hatching container. Eggs typically hatch in 6 to 8 days at 24 °C. The fry are tiny but free-swimming almost immediately. Feed them infusoria or a commercial liquid fry food for the first week, then graduate to freshly hatched baby brine shrimp. Keep the fry tank scrupulously clean with gentle sponge filtration and small daily water changes. Growth is steady, and young fish begin to show colour at around three to four months.

Common diseases and health

Madagascar Rainbows are generally robust, but they are not immune to common freshwater diseases, especially if water quality slips or new fish are introduced without quarantine.

Ich (white spot disease) is the most common issue. Look for tiny white spots on the body and fins, clamped fins, and fish rubbing against surfaces. Raise the temperature gradually to 28 °C and treat with a copper-based medication or a proprietary ich remedy following the manufacturer’s instructions. Most cases resolve within a week of treatment.

Fin rot can develop in response to poor water quality or physical damage from aggressive tankmates. Symptoms include frayed, discoloured, or eroding fin edges. Improve water quality immediately with extra water changes, and treat with an antibacterial medication such as Seachem Kanaplex if the condition does not improve within a few days.

Velvet (Piscinoodinium) is less common but worth watching for. It appears as a fine golden or rusty dust on the skin, often accompanied by laboured breathing and lethargy. Dim the lights, raise the temperature slightly, and treat with a copper-based medication. Velvet spreads quickly, so act fast if you suspect it.

Always quarantine new fish for at least two weeks in a separate tank before adding them to your main display. This simple step prevents the vast majority of disease introductions and is well worth the minor inconvenience.

Frequently asked questions

How many Madagascar Rainbows should I keep together?

Six is the minimum, but eight to twelve is better. A larger group spreads out male aggression, encourages natural behaviour, and results in much bolder, more colourful fish. Keeping fewer than six often leads to stress, skittishness, and faded colours.

Can Madagascar Rainbows live in a cold water tank?

They tolerate temperatures as low as 20 °C, which is cooler than many tropical fish, but they are not true cold water species. In most homes without central heating, a heater is still recommended to prevent temperature drops below 20 °C overnight or during winter months.

Do Madagascar Rainbows jump?

Yes, they can and do jump, especially when startled or during vigorous spawning activity. A tight-fitting lid or a mesh cover is essential. Even small gaps near filter intakes or airline tubing can be an escape route, so cover them.

Why are my Madagascar Rainbows losing colour?

Colour loss is almost always a sign of stress, poor water quality, inadequate diet, or too small a group size. Check your water parameters, ensure the school is at least six strong, and introduce more variety into their diet. Colour usually returns within a couple of weeks once conditions improve.

Are Madagascar Rainbows suitable for planted tanks?

Absolutely. They are one of the better rainbowfish for planted setups because they do not dig up substrate or eat most plant species. They may nibble on very soft-leaved plants occasionally, but robust species like Java fern, Anubias, and Vallisneria are left alone.

Related guides

• Madagascar Rainbow breeding guide
• Madagascar Rainbow tank setup and equipment guide
• Madagascar Rainbow diet and feeding guide
• Best tank mates for Madagascar Rainbow
• Madagascar Rainbow diseases and health guide
• Why is my Madagascar Rainbow losing colour?
• Back to the fish species directory
• Beginner’s guide to cycling your tank